My experience adding subwoofers to 2 channel


My Kappa 9 speakers are rated to 29hz and they sound pretty good in my 18x24 room...powered by McIntosh mc1.25 amps...l was looking for another layer of bass to enhance the sound..my first experiment l took my SVS pb16 ultras from my theater room and tried them first...it sounded terrible,didn't blend well..couldn't hear a difference until you turned in up then it rattled the room apart........my final experiment worked..l used 4 Velodyne minivee subwoofers(1000 watt rms class D sealed 8 in.) and after hours of calibration l hit it......lve got the bass response that exeeded my expectations. ....l should have done this along time ago....can anybody tell me of another subwoofer that may work even better?
128x128vinnydabully
Atmasphere, they were an undersung product but the company had trouble finding itself and was trying to be all things to all people.  Initially all the Acoustats used a "direct drive" high voltage tube amplifier. The first Model was the "X"  It was a beautiful 3 panel speaker with the amp mounted inside a plywood enclosure. Unfortunately it was very colored entirely due to the enclosure. They then moved to the Monitor series both three and four panel versions. It was the Monitor 4 which convinced me that they were on to something. It was with this speaker that I first played around with subwoofers. They then again redesigned the enclosures  to make them easier to manufacture. These were called the 1, 2, the 3, the 4 then the 1+1, 2+2, 3+3 and 4+4. They felt their sales were low because people wanted to use their own amps so they came up with a two transformer interface which was relatively easy to drive. There were two versions of this interface. The problem with this was that us audio types preferred the Direct Drive amp. The smaller speakers unaided by a subwoofer were not impressive. But the 2+2 was almost an entirely different animal. Given an amp like the Krell KMA 100 they not only had the magic ESL midrange but killer dynamics. Put them with a subwoofer and all hell broke loose. As big as they are they remain very selfish speakers. Very few 3+3s and 4+4s were made. They were just two big and you had to run two interfaces and two amps with each speaker. The 4+4s were the size of the Soundlabs Majestic 845. The most important item that Acoustat brought to the world was the first totally indestructible electrostatic panel. Quads had given ESLs a bad name because they were very fragile and I think Acoustat suffered because of that. My panels are now 40 years old. The 1/2 life of the plastic used in their construction is 50,000 years. Unless you drive a stake through them they will go on forever. If you have heard any of the larger SoundLabs then you have essentially heard the 2+2 but with a bit more dispersion. Most of these speakers have been cannibalized and the panels beaten up. 2+2s in serviceable condition are hard to find. The Company was eventually sold to David Hafler who went belly up some time later.
Panel speakers have gained more acceptance and I think there is room for a lower cost full range ESL like the 2+2. The individual panels might cost $50 to make if that. The frame maybe $100. The transformer/power supply another $100. $400 all told for a speaker you could sell all day long for $4000.............
 
Music Reference now offers an ESL with the option of a direct-drive (no ESL transformer) OTL power amp. MR's Roger Modjeski designed the same for the original Beveridge, and has custom made some d-d amps for Acoustats.
@bdp24, the Beveridge amps were not Roger's design, only the RM-1, RM-2, and RM-3 which mad up the rest of the components in the Beveridge system which if I recall was the 2SW.
@mijostyn I've heard the direct drive version- that speaker never seemed to bring home the bacon the way the one did that was easily driven by the M-60s (which replaced an ARC Classic 60; this was a good 15 years ago).
I wish I knew which model that was as I've heard Acoustats that looked just like it but needed a big amp to make them play. The first time I heard an Acoustat though I was very surprised at how well our amps and the speakers worked together. IMO they worked quite a bit better than the Quads, which at the time were also easy to drive.

By comparison the direct drive model had a bit of a trashy sound on top and we got better bass with the regular speaker (it had no hint of trashiness!). But I think there was a good possibility the power tubes in the direct drive model I heard were simply shot. That was a tricky speaker- you really had to be careful around it due to the very high plate voltage on the power tubes.

Of course I've heard Sound Labs many times. Something like 80% of all our MA-2 amplifier production has gone to Sound Lab owners.